1. Field of the Invention
The present invention relates to a vehicle door latch device and relates to, in particular, a lock actuator and a switch box of the latch device.
2. Description of the Related Art
A conventional door latch device has a motorized actuator for switching the latch device into a locked state and an unlocked state. Some of the actuator is directly installed on a rear surface or a bottom of a latch body of the latch device (as disclosed in, for example, U.S. Pat. No. 4,948,183), and most of the remainder is indirectly installed at the latch body using a metal bracket (as disclosed in, for example, U.S. Pat. No. 4,978,154 and U.S. Pat. No. 5,035,453).
Although the former latch device wherein the actuator is directly installed at the latch body has an advantage in that a bracket is not necessary as the latter is, it is sometimes more expensive than the latter one. This is due to the fact that the actuator of the former is designed exclusively for a certain latch body at which the actuator is to be installed. Besides, it is substantially impossible to use the exclusively designed actuator in a different type of a latch body. Therefore the typical actuator is installed at the latch body using the metal bracket as the latter.
The latter latch device typically comprises a latch body for accommodating a latch and a ratchet, a metal front plate installed at a front surface of the latch body, and a metal back plate installed at a rear surface of the latch body. The back plate includes a rear plate having a surface substantially parallel to the rear surface of the latch body, and an angled plate projecting backward from the rear plate. The actuator is fixed to the angled plate by screws. The latter latch device is thus aimed to cut costs by forming the bracket used for installation of actuator, integrally with the back plate.
The problem with the latter latch device is that it is difficult to ensure actuator installation strength. The actuator installed at the angled plate is swung more than expected by the metal elasticity of the angle plate and sometimes make a clattering noise. Due to this, it is required to improve the strength or rigidity of installation of the actuator using a reinforcing member independent of the angled plate, thereby raising manufacturing costs.
The conventional latch device has, meanwhile, a switch for detecting a position of the latch which is adapted to be rotated against a resilient force of a latch return spring by an engagement a striker fixed to a vehicle body (as disclosed in, for example, U.S. Pat. No. 5,678,869). A signal from the switch is utilized to control an interior light or room lamp of the vehicle, an ajar warning light and/or an ignition key light for illuminating a keyway or a keyhole of an ignition key cylinder.
Japanese U.M. Publications (Kokoku) Nos. 3-38374 and 6-40297 teach a handle assembly which has a handle base installed at an exterior door panel of a vehicle door, an exterior opening handle rotatably installed at the handle base, and a switch for detecting the rotation or operation of the opening handle. A signal from the switch is utilized to control a door key light for illuminating a keyway of a door key cylinder. With this structure, the keyway is illuminated by the operation of the door handle even in a dark place and is easily visible.
The latter switch, which is installed at the handle base, is required to be assembled independently of the assembly of the latch device. It is, however, possible to store the latter switch together with the former switch in a switch box installed at the latch device.